Merge pull request #4 from mengxr/ml-package-docs

replace TypeTag with explicit datatype

Author: jkbradley

mllib/src/main/scala/org/apache/spark/ml/Transformer.scala

@@ -18,16 +18,14 @@
 package org.apache.spark.ml
 
 import scala.annotation.varargs
-import scala.reflect.runtime.universe.TypeTag
 
 import org.apache.spark.Logging
 import org.apache.spark.annotation.AlphaComponent
 import org.apache.spark.ml.param._
 import org.apache.spark.sql.SchemaRDD
 import org.apache.spark.sql.api.java.JavaSchemaRDD
-import org.apache.spark.sql.catalyst.ScalaReflection
 import org.apache.spark.sql.catalyst.analysis.Star
-import org.apache.spark.sql.catalyst.dsl._
+import org.apache.spark.sql.catalyst.expressions.ScalaUdf
 import org.apache.spark.sql.catalyst.types._
 
 /**
@@ -86,7 +84,7 @@ abstract class Transformer extends PipelineStage with Params {
  * Abstract class for transformers that take one input column, apply transformation, and output the
  * result as a new column.
  */
-private[ml] abstract class UnaryTransformer[IN, OUT: TypeTag, T <: UnaryTransformer[IN, OUT, T]]
+private[ml] abstract class UnaryTransformer[IN, OUT, T <: UnaryTransformer[IN, OUT, T]]
   extends Transformer with HasInputCol with HasOutputCol with Logging {
 
   def setInputCol(value: String): T = set(inputCol, value).asInstanceOf[T]
@@ -99,6 +97,11 @@ private[ml] abstract class UnaryTransformer[IN, OUT: TypeTag, T <: UnaryTransfor
    */
   protected def createTransformFunc(paramMap: ParamMap): IN => OUT
 
+  /**
+   * Returns the data type of the output column.
+   */
+  protected def outputDataType: DataType
+
   /**
    * Validates the input type. Throw an exception if it is invalid.
    */
@@ -111,17 +114,16 @@ private[ml] abstract class UnaryTransformer[IN, OUT: TypeTag, T <: UnaryTransfor
     if (schema.fieldNames.contains(map(outputCol))) {
       throw new IllegalArgumentException(s"Output column ${map(outputCol)} already exists.")
     }
-    val output = ScalaReflection.schemaFor[OUT]
     val outputFields = schema.fields :+
-      StructField(map(outputCol), output.dataType, output.nullable)
+      StructField(map(outputCol), outputDataType, !outputDataType.isPrimitive)
     StructType(outputFields)
   }
 
   override def transform(dataset: SchemaRDD, paramMap: ParamMap): SchemaRDD = {
     transformSchema(dataset.schema, paramMap, logging = true)
     import dataset.sqlContext._
     val map = this.paramMap ++ paramMap
-    val udf = this.createTransformFunc(map)
-    dataset.select(Star(None), udf.call(map(inputCol).attr) as map(outputCol))
+    val udf = ScalaUdf(this.createTransformFunc(map), outputDataType, Seq(map(inputCol).attr))
+    dataset.select(Star(None), udf as map(outputCol))
   }
 }

mllib/src/main/scala/org/apache/spark/ml/feature/HashingTF.scala

@@ -21,7 +21,8 @@ import org.apache.spark.annotation.AlphaComponent
 import org.apache.spark.ml.UnaryTransformer
 import org.apache.spark.ml.param.{IntParam, ParamMap}
 import org.apache.spark.mllib.feature
-import org.apache.spark.mllib.linalg.Vector
+import org.apache.spark.mllib.linalg.{VectorUDT, Vector}
+import org.apache.spark.sql.catalyst.types.DataType
 
 /**
  * :: AlphaComponent ::
@@ -39,4 +40,6 @@ class HashingTF extends UnaryTransformer[Iterable[_], Vector, HashingTF] {
     val hashingTF = new feature.HashingTF(paramMap(numFeatures))
     hashingTF.transform
   }
+
+  override protected def outputDataType: DataType = new VectorUDT()
 }

mllib/src/main/scala/org/apache/spark/ml/feature/Tokenizer.scala

@@ -20,7 +20,7 @@ package org.apache.spark.ml.feature
 import org.apache.spark.annotation.AlphaComponent
 import org.apache.spark.ml.UnaryTransformer
 import org.apache.spark.ml.param.ParamMap
-import org.apache.spark.sql.{DataType, StringType}
+import org.apache.spark.sql.{DataType, StringType, ArrayType}
 
 /**
  * :: AlphaComponent ::
@@ -36,4 +36,6 @@ class Tokenizer extends UnaryTransformer[String, Seq[String], Tokenizer] {
   protected override def validateInputType(inputType: DataType): Unit = {
     require(inputType == StringType, s"Input type must be string type but got $inputType.")
   }
+
+  override protected def outputDataType: DataType = new ArrayType(StringType, false)
 }